Modern brake systems are usually controlled electronically. Therefore, various measured values are detected in the area of the brake system, including, for example, the wheel brake pressures, brake circuit pressures, driver intent signals such as pedal displacement, main cylinder displacements, admission pressures, etc. These measured quantities must be calibrated to a basic value to guarantee satisfactory control.
An electrically controlled brake system is described in German Patent Application No. 198 07 369, for example. In that patent, an intent to brake is deduced from the fact that the driver has operated the brake pedal and this is converted to setpoint brake pressures for the individual wheel brakes, taking into account additional operating quantities, if necessary. The setpoint brake pressures for the individual wheels or axles are regulated for each wheel or for each axle by pressure control circuits based on the respective setpoint pressure and the actual brake pressure measured in the area of the wheel brake. To determine the driver""s intent to brake, a pedal displacement sensor is provided. However, no measures are described for calibrating at least one of the measured quantities.
When the system is started, an automatic determination of the basic values is made possible through the procedure described below. No manual adjustment is necessary.
It is especially advantageous that the basic values are determined only when the system is in a suitable state for this purpose.
Changes during operation of the vehicle, depending on temperature or aging, for example, are detected in an advantageous manner and the respective basic values are corrected.